In mining operations, such as coal mining, a machine known as a shearer is used for excavating. The shearer, when used in longwall mining for example, has a rotating drum which carries a set of helically arranged cutting tools for cutting into the vein of coal. Each cutting tool is individually mounted on the drum, typically by a mounting block. The mounting block is provided with a socket which is adapted to receive the shank of a tool holder which carries a cutting bit.
In the prior art, the tool holder comprises a cylindrical shank adapted to be inserted into the socket of a mounting block, a conical head adapted to receive the tool bit, and a cylindrical section between the shank and the head. The shank is provided with an annular groove for receiving a retaining member to retain the tool holder in the block. The cylindrical section is provided with an annular groove for receiving an extracting tool for removal of the tool holder from the block. In the prior art, the tool holder of this type is made from a steel rod by machining, as by a lathe operation, to obtain the desired shape. The prior art tool holder has the disadvantage, not only of the high cost of the machining operation, but also a resulting structure which leaves room for improvement in strength and other properties.
A general object of this invention is to provide an improved mining bit tool holder which overcomes certain disadvantages of the prior art.